- ID:
- ivo://CDS.VizieR/J/A+A/425/417
- Title:
- Star formation rates of blue compact galaxies
- Short Name:
- J/A+A/425/417
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Halpha, [OII]3727, infrared (IR), radio (1.4GHz) luminosities and neutral hydrogen (HI) gas masses, we estimated star formation rates and gas depletion timescales of 72 star-forming blue compact galaxies (BCGs) To assess the possible systematic differences among different star formation rate indicators, we compared the star formation rates derived from Halpha, [OII]3727, IR, and radio luminosities, and investigated the effects from underlying stellar absorption and dust extinction. We found that subtracting underlying stellar absorption is very important to calculate both dust extinction and star formation rate of galaxies. Otherwise, the intrinsic extinction will be overestimated, the star formation rates derived from [OII]3727 and Halpha will be underestimated (if the underlying stellar absorption and the internal extinction were not corrected from the observed luminosity) or overestimated (if an overestimated internal extinction were used for extinction correction). After both the underlying stellar absorption and the dust extinction were corrected, a remarkably good correlation emerges among Halpha, [OII]3727, IR and radio star formation rate indicators.
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- ID:
- ivo://CDS.VizieR/J/A+A/601/A95
- Title:
- Star-forming dwarfs at intermediate-z in VUDS
- Short Name:
- J/A+A/601/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present emission line measurements and the main physical properties of a sample of 164 star-forming dwarf galaxies (SFDGs) in the VIMOS Ultra Deep Survey (VUDS, Le Fevre et al., 2015A&A...576A..79L). VUDS is one of the largest programs on the ESO-VLT with 640 hours of observing time, and covers a total of one square degree in three separate fields: COSMOS, ECDFS, and VVDS-02h. The spectroscopic observations were carried out at the VLT with the VIMOS Multi-Object Spectrograph (MOS) with two grisms (LRBLUE and LRRED) covering a wavelength range of 365<lambda<935nm at uniform spectral resolution of R=180 and R=210, respectively. The integration time (on-source) is ~14-hours per target for each grism, which allows to detect the continuum at 850nm for i_AB_=25, and emission lines with an observed flux limit F=1.5*10^-18^erg/s/cm2 at S/N~5. Redshift measurements in VUDS were performed using the EZ code (Garilli et al., 2010PASP..122..827G), both in automatic and manual modes (by two persons independently) for each spectrum. The overall redshift accuracy is dz/(1+z)=0.0005-0.0007. The spectra had already been fully calibrated in wavelength and flux by the VUDS team, which also did the sky subtraction. Emission lines fluxes and equivalent widths are measured manually on a one-by- one basis using the task 'splot' of IRAF by direct integration of the line profile after linear subtraction of the continuum. These fluxes are given in units of 10^-18^erg/s/cm^2^. The uncertainties in the line measurements were computed from the dispersion of values provided by multiple measurements adopting different possible band-passes (free of lines and strong residuals from sky subtraction) for the local continuum determination, which is fitted using a second order polynomial. No extinction correction has been applied to these fluxes. The EW measurements of H{gamma}, H{beta} and H{alpha} lines have been already corrected for absorption by +0.1nm for all galaxies, following Ly et al. (2014ApJ...780..122L). For each galaxy the reddening constant, c(H{beta}), is presented. These values and their uncertainties have been derived from the H{alpha}/H{beta} or H{gamma}/H{beta} ratios, whenever possible. We adopted the reddening constant from the best-fit SED, using the relations of Calzetti et al. (2000ApJ...533..682C), for (a) galaxies where the computation of c(H{beta}) from emission lines is not possible because the lines are not present, or (b) the line ratios give a negative extinction correction (i.e., H{alpha}/H{beta}<2.82 or H{gamma}/H{beta}<0.47, assuming Case B recombination with Te=2*10^4^K, ne=100cm^-3^).
- ID:
- ivo://CDS.VizieR/J/ApJ/773/86
- Title:
- Star-forming galaxies in ACO 2029
- Short Name:
- J/ApJ/773/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dense environments are known to quench star formation in galaxies, but it is still unknown what mechanism(s) are directly responsible. In this paper, we study the star formation of galaxies in A2029 and compare it to that of Coma, combining indicators at 24{mu}m, H{alpha}, and UV down to rates of 0.03M_{sun}_/yr. We show that A2029's star-forming galaxies follow the same mass-SFR relation as the field. The Coma cluster, on the other hand, has a population of galaxies with star formation rates (SFRs) significantly lower than the field mass-SFR relation, indicative of galaxies in the process of being quenched. Over half of these galaxies also host active galactic nuclei. Ram-pressure stripping and starvation/strangulation are the most likely mechanisms for suppressing the star formation in these galaxies, but we are unable to disentangle which is dominating. The differences we see between the two clusters' populations of star-forming galaxies may be related to their accretion histories, with A2029 having accreted its star-forming galaxies more recently than Coma. Additionally, many early-type galaxies in A2029 are detected at 24{mu}m and/or in the far-UV, but this emission is not directly related to star formation. Similar galaxies have probably been classified as star forming in previous studies of dense clusters, possibly obscuring some of the effects of the cluster environment on true star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/579/A80
- Title:
- Star-forming regions deuteration
- Short Name:
- J/A+A/579/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical evolution in high-mass star-forming regions is still poorly constrained. Studying the evolution of deuterated molecules allows distinguishing between subsequent stages of high-mass star formation regions based on the strong temperature dependence of deuterium isotopic fractionation. We observed a sample of 59 sources including 19 infrared dark clouds, 20 high-mass protostellar objects, 11 hot molecular cores and 9 ultra-compact HII regions in the (3-2) transitions of the four deuterated molecules, DCN, DNC, DCO^+^, and N_2_D^+^ as well as their non-deuterated counterparts. The overall detection fraction of DCN, DNC, and DCO^+^ is high and exceeds 50% for most of the stages. N_2_D^+^ was only detected in a few infrared dark clouds and high-mass protostellar objects. This may be related to problems in the bandpass at the transition frequency and to low abundances in the more evolved, warmer stages. We find median D/H ratios of 0.02 for DCN, 0.005 for DNC, 0.0025 for DCO^+^, and 0.02 for N_2_D^+^. While the D/H ratios of DNC, DCO^+^, and N_2_D^+^ decrease with time, DCN/HCN peaks at the hot molecular core stage. We only found weak correlations of the D/H ratios for N_2_D^+^ with the luminosity of the central source and the FWHM of the line, and no correlation with the H_2_ column density. In combination with a previously observed set of 14 other molecules (Paper I), we fitted the calculated column densities with an elaborate 1D physico-chemical model with time-dependent D-chemistry including ortho- and para-H_2_ states. Good overall fits to the observed data were obtained with the model. This is one of the first times that observations and modeling were combined to derive chemically based best-fit models for the evolution of high-mass star formation including deuteration.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/10
- Title:
- Star-forming z~2.1 galaxy metallicities
- Short Name:
- J/ApJ/817/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the evolution of the Stellar Mass-Star Formation Rate (SFR)-Metallicity relation using a set of 256 COSMOS and GOODS galaxies in the redshift range 1.90<z<2.35. We present the galaxies' rest-frame optical emission-line fluxes derived from IR-grism spectroscopy with the Hubble Space Telescope and combine these data with SFRs and stellar masses obtained from deep, multi-wavelength (rest-frame UV to IR) photometry. We then compare these measurements to those for a local sample of galaxies carefully matched in stellar mass (7.5<~log(M_{star}_/M_{sun}_<~10.5) and SFR (-0.5<~log(SFR)<~2.5 in M_{sun}_/yr). We find that the distribution of z~2.1 galaxies in stellar mass-SFR-metallicity space is clearly different from that derived for our sample of similarly bright (L_H{beta}_>3x10^40^erg/s) local galaxies, and this offset cannot be explained by simple systematic offsets in the derived quantities. At stellar masses above ~10^9^M_{sun}_ and SFRs above ~10M_{sun}_/yr, the z~2.1 galaxies have higher oxygen abundances than their local counterparts, while the opposite is true for lower-mass, lower-SFR systems.
2676. Stark broadening
- ID:
- ivo://CDS.VizieR/J/A+AS/113/579
- Title:
- Stark broadening
- Short Name:
- J/A+AS/113/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tables of Stark broadening profiles for the N V 6f, g, h-7f, g, h, i line complex at 4945A have been generated. Modern close-coupling techniques are used for the electron broadening while the important influence of perturbing ions is included within the framework of the model microfield method. Comparison has been made with the results of line formation calculations using approximate formulae for the Stark profiles.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/1736
- Title:
- Stark broadening of XeVIII spectral lines
- Short Name:
- J/MNRAS/454/1736
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stark broadening parameters have been calculated for 60 spectral lines of XeVIII, for broadening by electron, proton, and HeIII impacts. For calculations, the semiclassical perturbation approach in the impact approximation has been used. The widths and shifts are provided for temperatures from 20000 K to 500000 K and for an electron density of 10^17^/cm^3^. Obtained results have been used to study the influence of Stark broadening on spectral lines in DO white dwarf atmospheres and it has been found that exist broad layers where this broadening mechanism is dominant in comparison with thermal Doppler broadening.
- ID:
- ivo://CDS.VizieR/J/ApJS/153/523
- Title:
- Starless cores in CS(3-2) and DCO^+^(2-1) lines
- Short Name:
- J/ApJS/153/523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CS(3-2) and DCO^+^(2-1) observations of 94 starless cores and compare the results with previous CS(2-1) and N_2_H^+^(1-0) observations to study inward motions in starless cores. Eighty-four cores were detected in both CS and DCO^+^ lines. We identify 18 infall candidates based on observations of CS(3-2), CS(2-1), DCO^+^(2-1) and N_2_H^+^(1-0). The eight best candidates, L1355, L1498, L1521F, L1544, L158, L492, L694-2, and L1155C-1, each show at least four indications of infall asymmetry and no counterindications. Fits of the spectra to a two-layer radiative transfer model in ten infall candidates suggest that the median effective line of sight speed of the inward-moving gas is ~0.07km/s for CS(3-2) and ~0.04km/s for CS(2-1).
- ID:
- ivo://CDS.VizieR/J/A+A/622/A99
- Title:
- Starless MDCs of NGC6334 molecular spectra
- Short Name:
- J/A+A/622/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation of high-mass stars remains unknown in many aspects. Two families of models compete to explain the formation of high-mass stars. On the one hand, quasi-static models predict the existence of high-mass pre-stellar cores sustained by a high degree of turbulence. On the other hand competitive accretion models predict that high-mass proto-stellar cores evolve from low/intermediate mass proto-stellar cores in dynamic environments. The aim of the present work is to bring observational constraints at the scale of high-mass cores (~0.03pc). We targeted with ALMA and MOPRA a sample of 9 starless massive dense cores (MDCs) discovered in a recent Herschel/HOBYS study. Their mass and size (~110M_{sun}_ and r=0.1pc, respectively) are similar to the initial conditions used in the quasi-static family of models explaining for the formation of high-mass stars.We present ALMA 1.4mm continuum observations that resolve the Jeans length ({lambda}_Jeans_~0.03pc) and that are sensitive to the Jeans mass (M_Jeans_~0.65M_{sun}_) in the 9 starless MDCs, together with ALMA-^12^CO(2-1) emission line observations. We also present HCO^+^(1-0), H^13^CO+(1-0) and N_2_H^+^(1-0) molecular lines from the MOPRA telescope for 8 of the 9 MDCs. The 9 starless MDCs have the mass reservoir to form high-mass stars according to the criteria by Baldeschi et al. (2017MNRAS.466.3682B). Three of the starless MDCs are subvirialized with {alpha}_vir_~0.35, and 4 MDCs show sign of collapse from their molecular emission lines. ALMA observations show very little fragmentation within the MDCs. Only two of the starless MDCs host compact continuum sources, whose fluxes correspond to <3M_{sun}_ fragments. Therefore the mass reservoir of the MDCs has not yet been accreted onto compact objects, and most of the emission is filtered out by the interferometer. These observations do not support the quasi-static models for high-mass star formation since no high-mass pre-stellar core is found in NGC6334. The competitive accretion models, on the other hand, predict a level of fragmentation much higher than what we observe
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/3393
- Title:
- Stars and globulars in NGC4494
- Short Name:
- J/MNRAS/415/3393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive analysis of the spatial, kinematic and chemical properties of stars and globular clusters (GCs) in the 'ordinary' elliptical galaxy NGC 4494 using data from the Keck and Subaru telescopes. We derive galaxy surface brightness and colour profiles out to large galactocentric radii. We compare the latter to metallicities derived using the near-infrared Calcium Triplet. We obtain stellar kinematics out to ~3.5 effective radii.
